Who doesn’t like a nice long 512-bit message digest to confirm that the file they’re opening is secure? Cryptographic hash functions are one method of verification to insure file integrity between two parties (or as a signature or authentication code). The most commonly used hash verification is MD5 check sum (proven insecure). Apple uses SHA-1 for it’s package update manager (also likely insecure). But if you want to get deep, go with Whirlpool, and I’m not talking about appliances here, I’m talking about 512 bits of hash (the authors, Barreto & Rijmen have a page here). Ironclad and md5deep are two easy to use packages if you’re looking to implement Whirlpool under most *nix and Win 32/64 systems.